20561516644 has 12 divisors (see below), whose sum is σ = 36224149500. Its totient is φ = 10211759648.

The previous prime is 20561516639. The next prime is 20561516681. The reversal of 20561516644 is 44661516502.

It can be written as a sum of positive squares in 2 ways, for example, as 5589057600 + 14972459044 = 74760^2 + 122362^2 .

It is a junction number, because it is equal to n+sod(n) for n = 20561516597 and 20561516606.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17248999 + ... + 17250190.

It is an arithmetic number, because the mean of its divisors is an integer number (3018679125).

Almost surely, 2^20561516644 is an apocalyptic number.

It is an amenable number.

20561516644 is a deficient number, since it is larger than the sum of its proper divisors (15662632856).

20561516644 is a wasteful number, since it uses less digits than its factorization.

20561516644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34499342 (or 34499340 counting only the distinct ones).

The product of its (nonzero) digits is 172800, while the sum is 40.

The spelling of 20561516644 in words is "twenty billion, five hundred sixty-one million, five hundred sixteen thousand, six hundred forty-four".